Perth in 2013: another hot year

The Perth Metropolitan area had near-average rain and very-much-above average temperatures in 2013, and it was the third warmest year in 115 years of record for the Perth Metro site.

Rainfall: near average

Maximum temperature: very much above average

Minimum temperature: very much above average

Rainfall

Rainfall in 2013 was near average across the Perth metropolitan area with annual totals ranging from 600 mm to 900 mm on the islands and much of the coastal plain, to near 1200 mm in the hills. The year was comprised of: a near average January, a dry February, an above average autumn due to a wet March and wet May, a very dry start to winter with the driest June on record for many Perth sites, followed by a wet July to October period with record high September rainfall at a number of Perth metropolitan sites, a dry November and December.

Perth Metro recorded 782.4 mm in 2013 on 114 rain days, which is near the long-term average of 848.3 mm. The wettest month was August with 167.4 mm, whilst September was the second wettest for the year with 144.2 mm, and was the wettest September at Perth Metro for 40 years, since 146.0 mm was recorded in 1973. The total for the August and September period was 311.6 mm, the wettest August and September for 58 years, since a total of 359.7 mm was recorded in 1955. The driest month of 2013 at Perth Metro was February with 0.8 mm, though November only fell one day short of having its second rainless month since records began in 1876, foiled by a cold front and 10.2 mm on the 30th. Arguably of greater significance in terms of lack of rainfall, Perth Metro recorded only 44.0 mm in June, its second lowest June rainfall in 137 years of recording. The record of 24.6 mm was set in June 2006, Perth Metro's driest year on record.

Notable events

A middle level trough on 10 March produced the first significant rainfall of 2013 in the metropolitan area, followed by further moderate falls on the 14th.

A strong cold front triggered thunderstorms with strong winds and moderate to heavy rainfall across the Perth region on 8 May. Rottnest Island recorded a wind gust of 106 km/h and a daily rainfall total of 61.6 mm, which was Rottnest Island's wettest May day for 20 years, since 65.0 mm was recorded on 18 May 1993.

A series of cold fronts and associated cloudbands in July produced moderate to heavy falls in the metropolitan area on the 9th, 15th and 16th, 24th, and 26th and 27th. The cold front on the 16th produced a wind gust of 111 km/h at Rottnest Island, the strongest wind gust recorded in the Perth metropolitan area in 2013.

A slow moving cloudband and northwesterly winds ahead of an approaching cold front brought persistent showery conditions to Perth with moderate to heavy falls between 5 and 8 August. Bickley recorded a daily total of 80.2 mm on the 8th, which was the highest daily rainfall of 2013 in the Perth area, and the second wettest August day at Bickley in its 36 years of record. Perth Metro also recorded its wettest day of 2013 on the 8th with 45.4 mm. This event was the start of a wet spell in Perth with rainfall recorded on 15 consecutive days at Perth Metro between 5 and 19 August.

A deep trough near the west coast produced showers and thunderstorms in Perth on 7 September with moderate to heavy falls in the northern suburbs and in the hills.

A slow moving strong cold front and associated low brought isolated thunderstorms, strong winds, and showers to Perth on 13 and 14 September with moderate to heavy falls reported. Rottnest Island recorded a daily rainfall of 42.0 mm on the 14th, which was its wettest September day for 29 years. A series of cold fronts following this event produced persistent rainfall events with Perth Metro recording 12 consecutive rain days between 14 and 25 September. Signifcant storm surge was observed during cold fronts on the 21st and 22nd along with wind gusts to 107 km/h at Rottnest Island and wind damage in Perth, including as a result of a tornado in Maddington.

Perth Metro recorded 40 days without measureable rainfall from 21 October to 29 November, the longest dry spell for spring at Perth Metro since records began in 1876.

Maximum temperature

Annual maximum temperatures in 2013 were very much above average with a mean annual maximum close to 23 °C on the islands and in the hills, and generally between 25 °C and 26 °C for most coastal plain sites. Pearce RAAF in the northeastern suburbs recorded its warmest year in 49 years of record with a mean maximum of 26.5 °C, exceeding the previous record of 26.4 °C in 1972.

Across the Perth metropolitan area, almost all months in 2013 were either close to or warmer than normal, the exception being a below average March. January was near average, in spite of a relatively hot spell from the 5th to the 8th with temperatures in the mid-to-high thirties at most sites. February was hot, with a notable hot spell from the 8th to 13th with temperatures generally ranging from the mid-thirties to the low forties across Perth, whilst high thirties to low forties temperatures where also recorded at most Perth sites on the 20th and 21st. The highest temperature of the year in the Perth metropolitan area was 43.2 °C at Pearce RAAF on 21 February. Autumn was near average due to a cool March, a very warm April, particularly at the start of the month, with a number of sites experiencing their warmest April on record, and a near average May. Winter was above average due to a near average June and July, and a very mild August with a number of sites recording their highest August mean maxima on record. Spring was above average across the Perth area due to a near average September and October, and an above average November. December finished the year with another above average month, partly as a result of a hot spell from the 12th to the 16th where temperatures were in the high thirties and low forties.

Cool to cold days were uncommon during 2013 and were mostly confined to 30 May, 15 June, and 11 and 17 July, where maximum temperatures in Perth were generally in the mid-teens. The lowest maximum temperature of the year in the Perth metropolitan area was 11.6 °C at Bickley on both 30 May and 17 July.

Perth Metro observed an annual mean daily maximum temperature of 25.5 °C in 2013, which was its third hottest year in 115 years of record, behind the equal record hot years of 2012 and 2011. Remarkably, the last four years have been the four hottest in Perth Metro's 115 year recording history, the order being 2012 and 2011 (25.7 °C), 2013 (25.5 °C), and 2010 (25.3 °C). In terms of the individual months in 2013 at Perth Metro, February, April, August, and November all ranked in the top 5 hottest for their respective month, with February fourth highest on record; April, first; August, first; and November, second. Only March and May saw mean maximum temperatures below the long-term average. Perth Metro daily maximum temperatures in 2013 ranged from a high of 40.5 °C on 21 February, to a low of 14.6 °C on both 30 May and 17 July.

Minimum temperature

Mean daily minimum temperatures were very much above average in the Perth Metropolitan area in 2013 with departures from the long-term mean close to 1.0 °C. Annual mean minima ranged from near 16 °C on the offshore islands to generally between 12 °C and 14 °C on the coastal plain and in the hills.

For the individual months of 2013, most were either near average or above average in terms of mean minimum temperatures, with the exception of June and July, both of which saw below average mean minima at a number of Perth observation sites. In contrast, April, August, September, and November were the warmest on record for many sites for the respective months.

The lowest temperature of 2013 in the Perth area was -1.2 °C at Jandakot Aerodrome on 8 July, and the highest minimum temperature of the year was 29.0 °C at Gosnells City on 15 January, which was its equal warmest night in January in 20 years of record.

Perth Metro observed an annual mean daily minimum temperature of 13.7 °C during 2013, very much above the average of 12.7 °C. The warmest months in terms of overnight temperatures, were February, with a mean minimum of 19.4 °C, and January, with a mean minimum of 19.3 °C, whilst the coldest month was July with a mean minimum of 6.9 °C. Daily minimum temperatures at Perth Metro in 2013 ranged from a low of 1.4 °C on 18 July, to a high of 27.3 °C on 15 January.

Sunshine

The annual mean daily sunshine recorded at Perth Airport was 8.8 hours, which is equal the long-term average.

Notes

A Annual Climate Summary is prepared to list the main features of the weather in Perth using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at
9 am on Thursday 2 January 2014.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

Averages are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 10 years of record, as they cannot then be calculated reliably.
The median
is sometimes more representative than the
mean
of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
decile ranking
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a
percentage of the long-term mean.

The ACORN-SAT dataset
is being used for temperature area averages from December 2012 onwards.
The major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, rather than 1950,
and hence rankings are calculated using a larger set of years.